1. Field of the Invention
The present invention relates to a machining time estimating device for shortening the time required for estimating a machining time when a NC program is modified.
2. Description of the Related Art
An operator who creates or modifies a NC program may often want to check a machining time of the NC program as well as whether the NC program operates correctly after the NC program is created or modified.
This is because, when a machining is carried out by a target NC program, it is necessary to grasp the machining time in order to check when the preparation of the next machining is to be prepared or to estimate the number of works that can be processed on a fixed schedule or time to perform production planning.
In general, an operator repeats two operation of “creating or modifying an NC program” and “checking the execution time of the NC program” to optimize the NC program. Here, the followings may be used as a method of “checking the execution time of the NC program”.
(1) A target NC program is executed using an actual machine tool.
(2) The execution time calculated when the NC program is created by a CAD/CAM system is used.
(3) Software for estimating a machining time of the NC program is used.
Here, the method (1) requires time the same as the execution time of the NC program in order to check the machining time and requires the machine tool to be operated actually in order to check the machining time. Thus, there is a problem in that the machine tool is exclusively used. Moreover, the method (2) calculates the time required for movement from a tool moving distance and a command transfer rate. Thus, there is a problem in that an acceleration/deceleration speed taken into consideration during operation of a numerical controller is not included in the estimated machining time and the error in the estimated machining time increases.
In contrast, Japanese Patent Application Laid-Open No. 2012-93975 discloses a technique of estimating a machining time of an NC program as an example of the method (3). This technique can estimate the machining time at a higher speed and higher accuracy than the methods (1) and (2) described above.
However, in this technique, the target range of the “estimation of the machining time” of the NC program is all blocks ranging from the leading block of the NC program to the last block. Thus, there is a problem in that, when the NC program is long, the processing time for calculating the estimation result of the machining time also increases. Therefore, as illustrated in FIG. 14, even when only several blocks of an NC program are modified, the estimation processing time is always substantially the same. Thus, there is a problem, if the operations of “creating or modifying an NC program” and the operation of “estimating the machining time” are repeated several times in order to optimize the NC program, and when the NC program is long, in that the operation time consumed for optimization of the NC program increases remarkably.